cqvip:Objectives: To define the role of magnetic resonance imaging(MRI) and intraope rative electrophysiological recording in targeting the subthalamic nucleus (STN) in Parkinson’s disease and to determine accuracy of electrode placement. Patie nts and methods: We implanted 54 electrodes into the STN in 27 patients. Target planning was done by coordinate guidelines and visualising the STN on MRI and de fined in relation to the mid-point of the AC-PC line. Intraoperative microelec trode recording was used. We adjusted electrode positions for placement in the c entre of the STN electrical activity and verified this on postoperative MRI in 1 6 cases, which were fused to the preoperative images to measure actual error in electrode placement in the three axes. Results: Based on coordinate calculation and MRI localisation, the mean of the target was 11.5 mm lateral,2.5 mm posterio r and 4.1 mm inferior to the mid-point of the AC-PC line. Fifty good electroph ysiological recordings of the STN (average length 4.65 mm) were achieved and tar get point adjusted in 90%of lead placements. The mean of the final target after electrophysiological correction was 11.7 mm lateral,2.1 mm posterior, and 3.8 m m inferior to the mid-point. The distance from the centre of the electrode arte fact to the final target used after electrophysiological recording on the fused images was 0.48 mm, 0.69 mm, and 2.9 mm in the x, y, and zaxes, respectively. No postoperative MRI related complication was observed. Conclusion: Both direct vi sualisation of the STN on MRI and intraoperative electrophysiological recording are important in defining the best target. Individual variations exist in the lo cation of the STN target. Fewer tracks were required to define STN activity on t he side operated first. Our current stereotactic method of electrode placement i s relatively accurate.
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